Nuclear spin relaxation in ordered bimetallic chain compounds

TL;DR

This paper provides a theoretical interpretation of proton spin relaxation times in a one-dimensional ferrimagnetic chain, using spin-wave theory and quantum Monte Carlo methods, aligning well with experimental data.

Contribution

It introduces a quantum Monte Carlo-based calculation of spin relaxation rates in a ferrimagnetic chain, linking low-energy dispersion relations to relaxation behavior.

Findings

T_1^{-1} scales as H^{-1/2} at low fields

Theoretical results match experimental temperature and field dependence

Quadratic dispersion dominates low-energy physics in quantum ferrimagnets

Abstract

A theoretical interpretation is given to recent proton spin relaxation-time (T_1) measurements on NiCu(C_7H_6N_2O_6)(H_2O)_3$\cdot$2H_2O, which is an ideal one-dimensional ferrimagnetic Heisenberg model system of alternating spins 1 and 1/2. The relaxation rate T_1^{-1} is formulated in temrs of the spin-wave theory and is evaluated by the use of a quantum Monte Carlo method. Calculations of the temperature and applied-field (H) dependences of T_1^{-1} are in total agreement with the experimental findings. T_1 behaves as $T_1^{-1}\propto H^{-1/2}$, which turns out an indirect observation of the quadratic dispersion relations dominating the low-energy physics of quantum ferrimagnets.